Railway traffic controlling apparatus



Jan. 7, 1936. F. H. NICHOLSON RAILWAY TRAFFIC CONTROLLING APPARATUSFiled Oct. 20, 1952 I 0 T T f m & 2 w a 2 3. 3

Fmm? H/Wclzolson BY 22W H18 ATTORNEY.

Patented Jan. 7, 1936 RAILWAY TRAFFICQOONTROLLING g a APPARATUS Frank H.Nicholson, Edgewood, Pa., assignor to The Union Switch & Signal Company,Swiss vale, Pa, a corporation of Pennsylvania Application October 20,1932, Serial No. 638,700

3 Claims.

My invention relates to railway trafiic controlling apparatus, and morespecificallyto apparatus for the elimination of interference caused bypropulsion current harmonics or other foreign current withthe operationof the wayside signaling equipment.

I will describe one form of apparatus embodying my invention, and willthen point out the novel features thereof in claims.

The accompanying drawing is a diagrammatic view showing an alternatingcurrent track circuit and the associated wayside signaling apparatusembodying my invention.

Referring to the drawing, the rails. l and 2 of track section DE aresupplied with alternating current from the secondary winding of a tracktransformer T connected across the rails at one end of the tracksection, for the purpose of energizing the track relay R which isconnected across the rails at the other end of the section, and for theadditional purpose of supplying codedtrack circuit current for theoperation of locomotivecarried train control equipment. Track relay R is'of the two-element type which requires simultaneous energization ofboth windings 3 and 4 with current of the proper relative polarity foroperation.

If a rail of section D-E carries alternating propulsion current havingharmonics the frequency of which coincides with the track circuitfrequency, it may happen that the propulsion potential existing acrosstrack winding 3 of relay R will be of sufficient magnitude and of properphase relation to pick up relay R falsely, or to interfere with theproper operation of this relay in case the foreign current frequencyapproaches the track circuit frequency. In order to eliminate thepossibility of false pick up and to decrease the above interference inthe apparatus embodying my invention the polarity of the currentssupplied to track winding 3 as well as to local winding 4 of relay R isperiodically and simultaneously reversed, whereby this relay becomesincapable of attaining its energized position by the energization ofeither winding with steady alternating current.

As a means for periodically reversing the currents supplied to windings3 and 4, I have provided a flashing or oscillating type of relay FR,which when energized, causes contacts 5-6 and 5-! to become closedalternately, thereby supplying periodically reversed current from atransformer T having a mid-tap 8 on its secondary winding, to winding 4,and to winding 3 through the medium of transformer T and the rails I and2. The open circuit interval of contacts 5-6 and 5-'l is sufficientlyshort to prevent release of relay R during the pole-change interval, andthe closed circuit interval is sufiiciently short so that relay R willnot close its front contacts on but one such interval. This latterrequirement is for the purpose of preventing an intermittent pick-up ofrelay R in the event of foreign current in the track winding andpole-changed current in the local winding of this relay.

When section DE and the next section in adjvance are both unoccupied,approach relay V is energized over front contact 9 of relay R, andperiodically pole-changed steady alternating current is supplied torelay R and track section D--E over front contact H) of relay V. Whensection D-E becomes occupied, front contact 9 of relay R will open,deenergizing relay V, and energizing the code transmitter CT over backcontact II of relay V. The code transmitter CT is so designed thatcontact fingers I80, I20 and operate at a speed of I80, I20 and 8Dmovements per minute, respectively, periodically closing theirrespective front and back contacts to pole-change and also to code thecurrent supplied to rails I and 2 from transformer T The code speedeffective at any particular time is dependent upon traffic conditions insection DE and the section in advance, as determined by the signalselection apparatus, which is not shown for simplicity. It will beunderstood that in order to provide for operation of the locomotive cabsignaling equipment, the contacts of the code transmitter CT must be sodesigned that there is a proper time interval between reversals of thecurrent supplied to the track circuit for producing the off intervals ofthe code.

The track relay R is designed in such manner that it will pick up on thecoded current supplied torails I and 2, so that as soon as the trainleaves section DE, relay R will pick up, energizing relay V over frontcontact 9, and deenergizing the code transmitter CT at back contact ll.Therefore, periodically pole-changed and uncoded current supplied fromtransformer T will be restored to rails l and 2 for maintaining relay Rin its energized position.

It will be apparent that if the normal supply of current to winding 3 ofrelay R is interrupted for any reason, such as a rail broken or a trainoccupying section DE, it will not be possible for a foreign current,such as a harmonic current of the propulsion power, which is of constantrelative polarity to pick up this relay because of the periodic reversalof current in the local winding 4 of relay R.

To make certain that winding 4 will at all times be supplied withperiodically reversed current, I have provided the two-element checkingrelay CR having a local winding l2 supplied with alternating current ofconstant relative polarity from the same source BX--CX which suppliescurrent to transformers 'I and T the control winding I3 of relay CRbeing connected across winding 4 of relay R. As long as the current inwinding 4 continues to be periodically reversed, contact I4 of relay CRwill continue to alternately close its right and left-hand contacts,supplying direct current from a source BC, first to one and then to theother half of the primary winding of transformer T thereby causing analternating voltage to be applied across the input terminals ofrectifier Q which results in the energization of slow releasing relaySR. Relay SR. is sufficiently slow acting to bridge the open circuitinterval of contact M of relay CR, therefore, relay SR will remainenergized and will maintain the signal control circuit, over its frontcontact l5, in an operative condition until such time as winding 4 ofrelay R becomes deenergized or its current supply ceases to beperiodically reversed, whereupon relay SR will release and a restrictiveindication will be displayed by suitable signals controlled over frontcontact 5 of this relay.

Although I have shown the apparatus embodying my invention applied towayside signaling equipment suitable for use in connection with a codesystem of train control, the apparatus is equally well adapted to thecontrol of wayside signaling equipment without train control, or withany other suitable system of train control.

'Although I have herein shown and described only one form of apparatusembodying my invention, it is understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention.

7 Having thus described my invention, what I claim is:

1. In combination, a section of railway track, a two-element relayhaving one element connected across the rails at one end of saidsection, a source of current, means for supplying current from saidsource to the track rails at the other end of said section and to theother element of said relay, a pole-changer located between said sourceand said track for periodically reversing the current simultaneously toboth elements of said relay, and trafli'c governing means controlled bysaid relay effective when both elements of said relay are simultaneouslysupplied with said periodically reversed current.

2. In combination, a section of railway track, a two-element relayhaving one element connected across the rails at one end of saidsection, a source of current, means including a pole-changer forapplying periodically reversed potential from said source simultaneouslyacross the track rails at the other end of said section and across theother element of said relay, an auxiliary relay controlled by thepotential across said other element of the relay in such manner thatsaid auxiliary relay becomes energized when and only when the potentialacross said other element is periodically reversed, and trafliogoverning means controlled by said two-element relay as well as by saidauxiliary relay.

3. In combination, a section of railway track,-

a relay having two cooperating windings one of which receives currentfrom the rails of said section, a source of current, means including apolechanger for supplying periodically and simultaneously reversedcurrent to the track rails and to the other winding of said relay, andtrafiic governing means controlled by said relay and effective when andonly when both windings of the relay are supplied with current which isperiodically and simultaneously reversed.

FRANK H. NICHOLSON.

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